Compressor

ABSTRACT

A compressor includes a casing and a motor disposed inside the casing. The motor is welded to the casing at a plurality of weld positions. The motor includes a core, a coil, at least one insulating member and a gap. The core has an annular back yoke portion, a plurality of tooth portions projecting radially inwardly from the back yoke portion and a slot formed between the tooth portions adjacent to each other. The coil is disposed in the slot. The insulating member is disposed in the slot to insulate the coil from the core. The gap is provided between the back yoke portion and the insulating member.

TECHNICAL FIELD

The present invention relates to a compressor that joints a casing and amotor disposed inside the casing by welding at a plurality of weldpositions.

BACKGROUND ART

In relation to a method of fixing a motor in a casing of a compressor,various compressors are suggested in which a casing and a motor disposedin the casing are joined by means of welding (e.g., see PatentLiteratures 1 and 2).

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Unexamined Patent Publication No.    262192/2003 (Tokukai 2003-262192)-   [Patent Literature 2] Japanese Unexamined Patent Publication No.    255332/2007 (Tokukai 2007-255332)

SUMMARY OF INVENTION Technical Problem

However, jointing a back yoke portion to a casing by welding may cause aproblem that the welding heat is transferred to the back yoke portionthus melting an insulating member disposed in a slot. Such a problem isparticularly noticeable in a motor with concentrated winding. This isbecause the thickness of the back yoke portion of such a motor issmaller than that of a motor with distributed winding. This enables thewelding heat to be more easily transferred to the insulating member,thus causing the insulating member to be molten.

In view of the above problem, the present invention is made and it is anobject of the present invention to provide a compressor in which meltingof an insulating member disposed in a slot is restrained.

Technical Solution

A first aspect of the present invention is a compressor including: acasing and a motor disposed inside the casing, which is jointed to thecasing by welding at a plurality of weld positions, wherein the motorincludes: a core having an annular back yoke portion, a plurality oftooth portions projecting radially inwardly from the back yoke portion,and a slot formed between the tooth portions adjacent to each other; acoil disposed in the slot; at least one insulating member disposed inthe slot, which insulates the coil from the core; and a gap providedbetween the back yoke portion and the at least one insulating member.

In this compressor, the gap is provided between the back yoke portionand the insulating member. This restrains the welding heat from beingtransferred to the insulating member. As a result, the insulating memberis restrained from being molten.

A second aspect of the present invention is the compressor of the firstaspect of the present invention adapted so that a portion of the backyoke portion facing the slot is substantially in an arc-shape.

In the compressor, the portion of the back yoke portion facing the slotis formed in a substantially arc-shape. It is therefore unlikely thatthe insulating member is disposed along the surface of the back yokeportion, and a gap is easily formed between the back yoke portion andthe insulating member. The higher the Young's modulus of the insulatingmember, the less likely to have the insulating member disposed along theback yoke portion.

A third aspect of the present invention is the compressor of the firstor second aspect of the present invention adapted so that the at leastone insulating member is made of an aramid-based resin.

In the compressor, the insulating member is made of an aramid-basedresin whose Young's modulus is greater than PET which is a typicallyused material for the insulating member. This way, the insulating memberis hardly warped. Thus, in the slot, the insulating member is notdisposed along the back yoke portion, and the gap is formed between theback yoke portion and the insulating member. In other words, the gap forrestraining heat transfer to the insulating member is easily formedsimply by changing the material for the insulating member, without aneed of changing the shape of the core.

A fourth aspect of the present invention is the compressor of the firstor second aspect of the present invention adapted so that: the at leastone insulating member includes two or more insulating members which arelaminated to each other; and one of the insulating members closest tothe core is made of an aramid-based resin.

In the compressor, the reliability is improved by using, as a materialfor the insulating member closest to the core, an aramid-based resinwhich is excellent in the strength and the durability.

Further, by laminating a plurality of insulating members, the dielectricstrength is improved.

Further, the insulating member closest to the core is made of anaramid-based resin whose Young's modulus is greater than PET which is atypically used material for the insulating member. This way, theinsulating member is hardly warped. Thus, in the slot, a plurality ofinsulating members are not disposed along the back yoke portion, and thegap is formed between the back yoke portion and the insulating member.In other words, the gap for restraining heat transfer to the insulatingmember is easily formed simply by changing the material for theinsulating member, without a need of changing the shape of the core.

A fifth aspect of the present invention is the compressor of the fourthaspect of the present invention adapted so that at least one of theinsulating members disposed on an inner side of the insulating membermade of an aramid-based resin is made of a polyethylene terephthalatefilm.

In a compressor adopting an insulating member made of an aramid-basedresin, the insulating member is unlikely to be disposed along the shapeof the slot, due to a high elasticity of the aramid-based resin. Thismay lead to a problem that the insulating member is enwound at the timeof winding. In the above compressor however, a polyethyleneterephthalate film which is highly flexible and which is easily disposedalong the slot is disposed on the inner side of the insulating membermade of the aramid-based resin. This polyethylene terephthalate filmpresses the insulating member on the outer side, which is made of thearamid-based resin. The insulating member made of the aramid-based resinis therefore firmly disposed. This restrains the insulating member frombeing enwound at the time of winding.

Further, this is more advantageous in terms of cost, as compared with acase of laminating insulating members made of an aramid-based resin,because the polyethylene terephthalate film is lower in costs than aninsulating member made of an aramid-based resin.

A sixth aspect of the present invention is the compressor of any one ofthe first to fifth aspects of the present invention adapted so thatrecesses are formed in portions of the back yoke portion each facing theslot.

(1) With the provision of the recess to the compressor, the recess inthe compressor absorbs distortion due to expansion and contractionstress caused by the welding heat. Thus, deformation of the core isreduced. This realizes an even air gap between the core and the rotordisposed in the core, thus restraining imbalance in the magnetic flux.As a result, an electromagnetic exciting force is restrained, andvibration and noise attributed by the vibration are restrained.(2) Further, when the recess serves as a passage for an oil orrefrigerant, the coil is cooled down. Therefore, the compressor achievesa better efficiency and a better reliability of the coil.(3) Further, in the compressor, the electromagnetic vibration of themotor is absorbed by the recess. This restrains the vibration to betransmitted to the casing, thus keeping the noise and vibration low.

A seventh aspect of the present invention is the compressor of the sixthaspect of the present invention adapted so that each of the recesses isprovided only in a portion corresponding to corresponding one of theweld positions, relative to the up/down direction.

The provision of the recess disturbs the flow of a magnetic flux. Thiscompressor however minimizes such an influence by limiting the range inwhich the recess is provided.

An eighth aspect of the present invention is the compressor of the sixthor seventh aspect of the present invention adapted so that, in a planview, each of the recesses extends in a direction crossing the radialdirection, and is formed in such a manner that the recess is narrowedtowards its both end portions relative to the direction crossing theradial direction, or that the both end portions have a circular shape.

The provision of the recess disturbs the flow of a magnetic flux. In thecompressor however, the flow of the magnetic flux is smoothened and theinfluence of the recess is restrained by forming the recess in such amanner that the recess is narrowed towards its end portions or that theend portions of the recess have a circular shape.

A ninth aspect of the present invention is the compressor of any one ofthe sixth to eighth aspects of the present invention adapted so that:the casing has a weld hole which is provided to each of the weldpositions; and in a plan view, the width of the recess relative to thedirection crossing the radial direction is greater than the width of theweld hole relative to the direction crossing the radial direction.

In the compressor, the recess covers the range in which thewelding-related heat radiates. Thus, a broad range of a portion of theinsulating member which may be molten is covered by the recess.

A tenth aspect of the present invention is the compressor of any one ofthe sixth to ninth aspects of the present invention adapted so that eachslot has more than one recesses.

In the compressor, the insulating member disposed in the slot issupported by a portion between the adjacent recesses, therefore it ispossible to prevent the insulating member from being warped even with aprovision of the recess.

An eleventh aspect of the present invention is the compressor of any oneof the first to tenth aspects of the present invention adapted so thatthe winding method of the coil is a concentrated winding.

In a motor with a concentrated winding, the width of the back yokeportion relative to a radial direction is smaller than that of a motorwith a distributed winding. Therefore, the problem that the insulatingmember may be molten is particularly noticeable in the motor of aconcentrated winding. For this reason, the present invention restrainingheat transfer to the insulating member is particularly effective for acompressor having a coil whose winding method is a concentrated winding.

A twelfth aspect of the present invention is the compressor of any oneof the first to eleventh aspects of the present invention adapted sothat a CO₂ refrigerant is used.

In a compressor adopting a CO₂ refrigerant, the motor and the casing aretypically jointed to each other by welding at a plurality of weldpositions. For this reason, the present invention restraining heattransfer to the insulating member is particularly effective for such acompressor adopting a CO₂ refrigerant.

Advantageous Effects of Invention

The present invention described hereinabove brings about the followingeffects.

With the first aspect of the present invention, the gap is providedbetween the back yoke portion and the insulating member. This restrainsthe welding heat from being transferred to the insulating member. As aresult, the insulating member is restrained from being molten.

With the second aspect of the present invention, the portion of the backyoke portion facing the slot is formed in a substantially arc-shape. Itis therefore unlikely that the insulating member is disposed along thesurface of the back yoke portion, and a gap is easily formed between theback yoke portion and the insulating member. The higher the Young'smodulus of the insulating member, the less likely to have the insulatingmember disposed along the back yoke portion.

With the third aspect of the present invention, the insulating member ismade of an aramid-based resin whose Young's modulus is greater than PETwhich is a typically used material for the insulating member. This way,the insulating member is hardly warped. Thus, in the slot, theinsulating member is not disposed along the back yoke portion, and thegap is formed between the back yoke portion and the insulating member.In other words, the gap for restraining heat transfer to the insulatingmember is easily formed simply by changing the material for theinsulating member, without a need of changing the shape of the core.

With the fourth aspect of the present invention, the reliability of thecompressor is improved by using, as a material for the insulating memberclosest to the core, an aramid-based resin which is excellent in thestrength and the durability.

Further, by laminating a plurality of insulating members, the dielectricstrength is improved.

Further, the insulating member closest to the core is made of anaramid-based resin whose Young's modulus is greater than PET which is atypically used material for the insulating member. This way, theinsulating member is hardly warped. Thus, in the slot, a plurality ofinsulating members are not disposed along the back yoke portion, and thegap is formed between the back yoke portion and the insulating member.In other words, the gap for restraining heat transfer to the insulatingmember is easily formed simply by changing the material for theinsulating member, without a need of changing the shape of the core.

With the fifth aspect of the present invention, a polyethyleneterephthalate film which is highly flexible and which is easy to disposealong the shape of the slot is disposed on the inner side of theinsulating member made of the aramid-based resin. This polyethyleneterephthalate film presses the insulating member on the outer side,which is made of the aramid-based resin. The insulating member made ofthe aramid-based resin is therefore firmly disposed. This restrains theinsulating member from being enwound at the time of winding.

Further, this is more advantageous in terms of cost, as compared with acase of laminating insulating members made of an aramid-based resin,because the cost of the polyethylene terephthalate film is lower thanthat of an insulating member made of an aramid-based resin.

Further, (1) With the provision of the recess to the compressor of thesixth aspect of the present invention, the recess in the compressorabsorbs distortion due to expansion and contraction stress caused by thewelding heat. Thus, deformation of the core is reduced. This realizes aneven air gap between the core and the rotor disposed in the core, thusrestraining imbalance in the magnetic flux. As a result, anelectromagnetic exciting force is restrained, and vibration and noiseattributed to the vibration are restrained. (2) Further, when the recessserves as a passage for an oil or a refrigerant, the coil is cooleddown. Therefore, the compressor achieves a better efficiency and abetter reliability of the coil. (3) Further, in the compressor, theelectromagnetic vibration of the motor is absorbed by the recess. Thisrestrains the vibration to be transmitted to the casing, thus keepingthe noise and vibration low.

With the seventh aspect of the present invention, disturbance to theflow of the magnetic flux is minimized by limiting the range in whichthe recess is provided.

Further, in the eighth aspect of the present invention, the recess isformed in such a manner that that the recess is narrowed toward its bothend portions, or that the end portions of the recess are formed in acircular shape. This smoothen the flow of the magnetic flux, anddisturbance to the flow of the magnetic flux is restrained.

Further, with the ninth aspect of the present invention, the recesscovers the range in which the welding-related heat radiates. Thus, abroad range of a portion of the insulating member which may be molten iscovered by the recess.

Further, in the tenth aspect of the present invention, the insulatingmember disposed in the slot is supported by a portion between theadjacent recesses, therefore it is possible to prevent the insulatingmember from being warped even with a provision of the recess.

In a motor of a concentrated winding which is related to the eleventhaspect of the present invention, the width of the back yoke portion in aradial direction is small. Therefore, the problem that the insulatingmember may be molten is particularly remarkable in the motor of aconcentrated winding. For this reason, the present invention restrainingheat transfer to the insulating member is particularly effective for acompressor having a coil whose winding method is a concentrated winding.

In a compressor of which adopts a CO₂ refrigerant such as the onerelating to the twelfth aspect of the present invention, the motor andthe casing are typically jointed to each other by welding at a pluralityof weld positions. For this reason, the present invention restrainingheat transfer to the insulating member is particularly effective forsuch a compressor adopting a CO₂ refrigerant.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view showing an internal structure of arotary compressor for a CO₂ refrigerant, in relation to a firstembodiment of the present invention.

FIG. 2 is a horizontal cross sectional view of the compressor.

FIG. 3 is a plan view of the motor.

FIG. 4 is an partially enlarged view of a stator.

FIG. 5 is a plan view of a core.

FIG. 6 is a partially enlarged view of a stator, in relation to a secondembodiment of the present invention.

FIG. 7 is a schematic cross sectional view of a motor and a pipe whichindicates positional relation between a weld position and a recess.

FIG. 8 is a partially enlarged view of a stator, in relation to a firstvariation of the second embodiment of the present invention.

FIG. 9 is a partially enlarged view of a stator, in relation to a secondvariation of the second embodiment of the present invention.

FIG. 10 is a partially enlarged view of a stator, in relation to a thirdvariation of the second embodiment of the present invention.

FIG. 11 is a partially enlarged view of a stator, in relation to a thirdembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes with reference to the attached drawingsembodiments of a rotary compressor for a CO₂ refrigerant, according tothe present invention.

First Embodiment

FIG. 1 is a cross sectional view showing an internal structure of arotary compressor for a CO₂ refrigerant, which relates to a firstembodiment of the present invention. FIG. 2 is a horizontal crosssectional view of the compressor. FIG. 3 is a plan view of the motor.FIG. 4 is an partially enlarged view of a stator. FIG. 5 is a plan viewof a core. With reference to FIG. 1 to FIG. 5, the following describes acompressor 1 related to the first embodiment of the present invention.

<Overall Structure of Rotary Compressor>

As shown in FIG. 1, a rotary compressor 1 of the first embodiment is a 2cylinder rotary compressor and includes: a sealed casing 10; a motor 20and a compression mechanism 3 disposed inside the sealed casing 10; andan accumulator 40 disposed on a side of the sealed casing 10. Thisrotary compressor 1 is a compressor of a high-pressure dome type, anduses a CO₂ refrigerant (hereinafter, simply referred to as refrigerant).In the rotary compressor 1, the compression mechanism 30 is disposedunder the motor 20 within the sealed casing 10. Further, in an underpart of the sealed casing 10 is stored lubricating oil 50 to be suppliedto each slide portion of the compression mechanism 30.

<Sealed Casing>

The sealed casing 10 is structured by a pipe 11, a top 12, and a bottom13. The pipe 11 is a substantially cylindrical member extended inup/down directions, whose upper and lower ends are opened. Further, on aside face of the pipe 11 are formed two connection ports 11 a and 11 bthrough which later-mentioned inlet tubes 43 a and 43 b are introducedto the inside of the sealed casing 10. These connection ports 11 a and11 b are aligned in the up/down directions. The inner circumferences ofthe connection ports 11 a and 11 b are connected to cylindrical jointtubes 14 a and 14 b which hold the inlet tubes 43 a and 43 b,respectively. The top 12 is a member for closing an opening at the upperend of the pipe 11. To the top 12 is attached a discharge pipe 15 whichejects a high-temperature and high-pressure refrigerant compressed bythe compression mechanism 30 to the outside of the sealed casing 10.Further, the top 12 is provided with a terminal 16 to be connected tothe motor 20. The bottom 13 is a member for closing an opening at thelower end of the pipe 11. The sealed casing 10 structured as describedwith the pipe 11, the top 12 and the bottom 13 forms a sealed space.

In the present embodiment, the motor 20 is disposed inside the pipe 11,and the pipe 11 and the motor 20 are spot welded to each other at threeweld positions P1 to P3, as shown in FIG. 2. In portions of the pipe 11corresponding to the three weld positions P1 to P3, the weld holes 10 ato 10 c are provided respectively. These weld positions P1 to P3 and theweld holes 10 a to 10 c are provided at intervals of 120 degrees alongthe circumference (in R directions). In an compressor 1 using a CO₂refrigerant, the pipe 11 and the motor 20 are typically fixed to eachother by welding.

<Motor>

The motor 20 is a motor whose winding method is a concentrated winding,in which coils 72 of phases (U phase, V phase, W phase) are formed atthe tooth portion 76 of the core 71. This motor 20 is provided to drivethe compression mechanism 30 disposed below, and includes a rotor 60 anda stator 70 disposed radially outward of the rotor 60 with an air gapbetween the stator 70 and the rotor 60, as shown in FIG. 3.

<Rotor>

The rotor 60 has a core 61 and a plurality of permanent magnets 62. Thecore 61 is formed by laminating a plurality of thin metal plates andwelding these plates to one another. Further, the core 61 has, atsubstantially its center, a through hole 63 having substantially acircular shape in a plan view. Into this through hole 63 is inserted anupper end portion of a shaft 80. This shaft 80 is fixed to the core 61.

<Stator>

As shown in FIG. 2 and FIG. 3, the stator 70 has a core 71, a coil 72, aslot cell (insulating member) 73, and insulators 74 a and 74 b (see FIG.1).

<Core>

The core 71 is formed by laminating a plurality of thin metal plates andwelding these plates to one another. As shown in FIG. 4 and FIG. 5, thecore 71 has an annular back yoke portion 75; nine tooth portions 76which project inwardly in a radial direction (X-direction) from the backyoke portion 75, and nine slots 77 formed between tooth portions 76. Thecore 71 has, at substantially its center portion, a through hole Hextended in the up/down directions. Inside this through hole H isdisposed a rotor 60 (see FIG. 3). Note that, in the motor 20 with thecoil 72 adopting a concentrated winding as its winding method, the widthof a back yoke portion 75 in a radial direction (X-direction) is smallerthan that of a motor whose coil adopts a distributed winding as itswinding method.

On the outer circumference of the back yoke portion 75, there are arcportions 75 a each contacting the inner circumference of the pipe 11,and core cut portions 75 b not contacting the inner circumference of thepipe 11. The arc portions 75 a and the core cut portions 75 b arealternately disposed along the circumference (in the R directions). Eacharc portion 75 a is curved so as to be disposed along the innercircumference of the pipe 11, while each core cut portion 75 b is formedto have a flat surface. In the present embodiment, the slot 77 isprovided on the inner side of the arc portion 75 a in the radialdirection (X-direction), while the tooth portion 76 is formed on theinner side of the core cut portion 75 b in the radial direction(X-direction). Further, the weld positions P1 to P3 are provided to thearc portions 75 a which contact the inner circumference of the pipe 11.On the other hand, between the core cut portion 75 b and the innercircumference of the pipe 11, a gap Q (see FIG. 4) is formed. Portionsof the inner circumference of the back yoke portion 75 each facing theslot 77 are formed in an arc-shape.

As shown in FIG. 2, coils 72 of phases (U phase, V phase, W phase) arewound at the nine tooth portions 76. Specifically, coils 72 of the Uphase, the V phase, and the W phase are wound in this order at the toothportions 76 along the circumference (in the R direction).

The nine slots 77 penetrate the cores 71 in the up/down directions (Zdirection), respectively. Further, each of the nine slots 77 are incommunication with the through hole H via an opening 77 a (see FIG. 4)formed between the tooth portions 76 adjacent to each other. Throughthis opening 77 a, a nozzle (not shown) of a winding machine is insertedinto the slot 77 to wind the coil 72 around the tooth portion 76.

Here, in the present embodiment, a slot cell 73 (0.1 mm to 0.5 mm inthickness) for insulating the tooth portion 76 and the coil 72 isinserted in the slot 77, as shown in FIG. 4. The slot cell 73 is made ofan aramid-based resin whose Young's modulus is greater than PET(polyethylene terephthalate) which is more typically used as thematerial for the slot cell. Therefore, a portion of the slot cell 73facing the inner circumference of the back yoke portion 75 extendsstraight in a direction (Y-direction) perpendicularly crossing theradial direction (X-direction), instead of being formed in an arc-shapethat is disposed along the inner circumference of the back yoke portion75. This way, a gap S1 is formed between the inner circumference of theback yoke portion 75 and the portion of the slot cell 73 facing theinner circumference. This gap S1 is reduced towards its both endportions relative to the direction (Y-direction) perpendicularlycrossing the radial direction (X-direction). Thus, the slot cell 73 doesnot contact the back yoke portion 75 while contacting the tooth portion76.

Note that the “aramid-based” means a polyamide fiber in the aromaticseries.

<Shaft>

As shown in FIG. 1, the shaft 80 rotates along with the rotor 60 thusrotating the pistons 34 and 37 of the compression mechanism 30. Thisshaft 80 has an eccentric portion 81 which is positioned in a cylinderchamber T1 of a later-mentioned front cylinder 33, and an eccentricportion 82 which is positioned in a cylinder chamber T2 of a rearcylinder 36. To these eccentric portions 81 and 82 are mounted pistons34 and 37, respectively. With the rotation of the shaft 80, the piston34 mounted to the eccentric portion 81 rotates in the cylinder chamberT1, and the piston 37 mounted to the eccentric portion 82 rotates in thecylinder chamber T2. Note that the respective positions of the eccentricportion 81 and the eccentric portion 82 are displaced by 180° in therotation direction of the shaft 80.

<Compression Mechanism>

As shown in FIG. 1, the compression mechanism 30 has a front muffler 31having a double structure, a front head 32, the front cylinder 33 andthe piston 34, a middle plate 35, a rear cylinder 36 and the piston 37,a rear head 38, a rear muffler 39, sequentially in this order from topto the bottom along the rotational axis of the shaft 80 of the motor 20.

The front muffler 31 ejects to a primary space the refrigerant ejectedfrom an ejection port (not shown) provided to the front head 32, whilereducing the noise. This front muffler 31 is attached to the front head32.

The front head 32 is jointed to an upper surface of the front cylinder33, and closes an opening at the upper end of the cylinder chamber T1.The front head 32 is provided with an ejection port (not shown) fromwhich the refrigerant compressed in the cylinder chamber T1 is ejectedto a muffler space M formed by the front muffler 31.

The front cylinder 33 is provided with the cylinder chamber T1 at itscenter portion. In the cylinder chamber T1 is disposed the piston 34which rotates eccentrically with rotation of the shaft 80. This cylinderchamber T1 is in communication with the muffler space M via theabove-mentioned ejection port. Thus, the refrigerant compressed byeccentric rotation of the piston 34 mounted to the eccentric portion 81of the shaft 80 is guided from the cylinder chamber T1 to the mufflerspace M.

The piston 34 rotates eccentrically along the inner circumference of thecylinder chamber T1 thus compressing the refrigerant sucked in from theaccumulator 40.

The middle plate 35 is disposed between the front cylinder 33 and therear cylinder 36. This middle plate 35 closes the opening at the lowerpart of the cylinder chamber T1 in the front cylinder 33 as well as theopening at the upper portion of the cylinder chamber T2 of the rearcylinder 36.

Descriptions regarding the rear cylinder 36, the piston 37, the rearhead 38, and the rear muffler 39 are omitted as these members functionssimilarly to those of the front cylinder 33, the piston 34, the fronthead 32, and the front muffler 31, respectively. Note that therefrigerant compressed in the cylinder chamber T2 of the rear cylinder36 is guided to the muffler space M via a communication hole (not shown)which is in communication with the rear head 38, the rear cylinder 36,the middle plate 35, and the front cylinder 33, and an introduction port(not shown) formed on the front head 32, after the refrigerant passes amuffler space (not shown) formed by the rear head 38 and the rearmuffler 39.

<Accumulator>

The accumulator 40 is provided for supplying a refrigerant from theoutside of the sealed casing 10 into the cylinder chamber T1 of thefront cylinder 33 and the cylinder chamber T2 of the rear cylinder 36.As shown in FIG. 1, the accumulator 40 has an entrance tube 41 extendedin a vertical direction, and two exit tubes 42 a and 42 b which are bentsubstantially in an L-shape. This way, the refrigerant flowing in fromthe entrance tube 41 is supplied to the cylinder chambers T1 and T2,through exit tubes 42 a and 42 b.

To the leading ends of the exit tubes 42 a and the 42 b are connectedsubstantially cylindrical inlet tubes 43 a and 43 b, respectively. Theseinlet tubes 43 a and 43 b are connected to the cylinders 33 and 36 viathe joint tubes 14 a and 14 b jointed to the sealed casing 10,respectively.

[Characteristics of the Compressor of the Present Embodiment]

The compressor 1 of the present embodiment has the followingcharacteristics.

In the compressor 1 of the present embodiment, the gap S1 is providedbetween the back yoke portion 75 and the slot cell 73. This restrainsthe welding heat from transferring to the slot cell 73. As a result, theslot cell 73 is kept from being molten.

Further, in the compressor 1 of the present embodiment, the slot cell 73is made of an aramid-based resin whose Young's modulus is greater thanPET which is a typically-adopted material. The slot cell 73 therefore isless likely to be warped. Thus, the slot cell 73 is not disposed alongthe back yoke portion 75 in the slot 77, and the gap S1 is formedbetween the back yoke portion 75 and the slot cell 73. In other words,the gap S1 for restraining heat transfer to the slot cell 73 is easilyformed simply by changing the material for the slot cell 73, without aneed of changing the shape of the core 71.

Further, in the compressor 1 of the present embodiment, the portion ofthe back yoke portion 75 facing the slot 77 is formed in a substantiallyarc-shape. It is therefore very unlikely that the slot cell 73 isdisposed along the surface of the back yoke portion 75, and the gap S1is easily formed between the back yoke portion 75 and the slot cell 73.In particular, the higher the Young's modulus of the slot cell 73, theless likely to have the slot cell 73 disposed along the back yokeportion 75.

In a compressor with a coil adopting a concentrated winding as itswinding method, the width of the back yoke portion 75 relative to theradial direction (X-direction) is smaller than that of the motor with adistributed winding. For this reason, the problem of melting the slotcell 73 particularly takes place in such a coil adopting theconcentrated winding. The compressor 1 aimed at restraining the heattransfer to the slot cell 73 therefore is particularly advantageous.

Further, in a compressor adopting a CO₂ refrigerant, the casing and themotor are typically jointed to each other by welding. The compressor 1aimed at restraining the heat transfer to the slot cell 73 therefore isparticularly advantageous.

Second Embodiment

FIG. 6 is a partially enlarged view of a stator, in relation to a secondembodiment of the present invention. FIG. 7 is a schematic crosssectional view of a motor and a pipe which indicates positional relationbetween a weld position and a recess. The following describe acompressor related to the second embodiment of the present invention,with reference to FIG. 6 and FIG. 7. In the first embodiment, the gap isformed between the back yoke portion 75 and the slot cell 73, byadopting an aramid-based material for the slot cell 73. The secondembodiment deals with a case where a gap is formed between the slot cell173 and the back yoke portion 175, by forming a recess S11 on a portionof the back yoke portion 175 facing the slot 177. The second embodimentis the same as the first embodiment except in the structure of thestator 170. Therefore, the descriptions are omitted as needed.

<Core>

The core 171 is formed by laminating a plurality of thin metal platesand welding these plates to one another. As shown in FIG. 6, the core171 has an annular back yoke portion 175, a plurality of tooth portions176 each projecting inwardly from the back yoke portion 175 in a radialdirection (X-direction), and a slot 177 formed between tooth portions176 adjacent to each other.

On the outer circumference of the back yoke portion 175, there are arcportions 175 a each contacting the inner circumference of the pipe 11,and core cut portions 175 b not contacting the inner circumference ofthe pipe 11. The arc portions 175 a and the core cut portions 175 b arealternately disposed along the circumference (in the R direction). Inthe present embodiment, the slot 177 is provided on the inner side ofthe arc portion 175 a relative to the radial direction (X-direction),and the tooth portions 176 is provided on the inner side of the core cutportion 175 b relative to the radial direction (X-direction). Further,the weld position P11 is provided to the arc portion 175 a whichcontacts the inner circumference of the pipe 11. On the other hand,between the core cut portion 175 b and the inner circumference of thepipe 11, a gap Q is formed.

In the present embodiment, the back yoke portion 175 has a recess S11 atits portion which corresponds to the weld position P11 and which facesthe slot 177. This recess S11 is provided between the weld position P11and the slot 177 nearby the weld position P11. In a plan view, therecess S11 extends in a direction (Y-direction) perpendicularly crossingthe radial direction (X-direction). The length L11 (Y-direction) of therecess S11 is greater than the width L2 of the weld hole 10 a relativeto the Y-direction.

Further, in the present embodiment, the above described recess S11 isprovided only in a portion corresponding to the weld position P11relative to the up/down direction (Z-direction), as shown in FIG. 7. Inother words, the recess S11 is provided to the same height as that ofthe weld position P11.

In the slot 177 is inserted a slot cell 173 for insulating the toothportions 176 and the coil 172. Unlike the slot cell 73 of the firstembodiment made of the aramid-based resin, the slot cell 173 (0.1 mm to0.5 mm in thickness) is made of PET whose Young's modulus is smallerthan that of the aramid-based resin. Although a portion of the slot cell173 facing the inner circumference of the back yoke portion 175 contactsthe inner circumference of the back yoke portion 175 in the presentembodiment, the recess S11 is formed on the inner circumference of theback yoke portion 175. This forms the gap S12 between the innercircumference of the back yoke portion 175 and the inner circumferenceof the slot cell 173.

[Characteristics of the Compressor of the Present Embodiment]

The compressor of the present embodiment has the followingcharacteristics.

With the provision of the recess S11, the gap S12 in the compressor ofthe present embodiment absorbs distortion due to expansion andcontraction stress caused by the welding heat. Thus, deformation of thecore 171 is reduced. This realizes an even air gap between the core 171and the rotor (see FIG. 3) disposed in the core 171, thus restrainingimbalance in the magnetic flux. As a result, an electromagnetic excitingforce is restrained, and vibration and noise attributed to the vibrationare restrained.

Further, when the recess S11 serves as a passage for an oil or arefrigerant, the coil 172 is cooled down. Therefore, the compressor ofthe present embodiment achieves a better efficiency and a betterreliability of the coil 172.

Further, in the compressor of the present embodiment, theelectromagnetic vibration of the motor is absorbed by the gap S12. Thisrestrains the vibration to be transmitted to the pipe 11, thus keepingthe noise and vibration low.

Further, in the compressor of the present embodiment, the recess S11 isprovided to only a portion corresponding to the weld position P11relative to the up/down direction (Z-direction). Limiting the range inwhich the recess S11 is provided minimizes a negative influence of therecess S11 to the flow of the magnetic flux.

Further, in the compressor of the present embodiment, the length L11 ofthe recess S11 relative to the direction (Y-direction) whichperpendicularly crosses the radial direction (X-direction) is greaterthan the length L2 of the weld hole 10 a in the same direction, in aplan view. This way the recess S11 covers the range in which thewelding-related heat radiates. Thus, the recess S11 covers a broad rangeof a portion of the slot cell 73 which may be molten.

Variation

FIG. 8 is a partially enlarged view of a stator which relates to a firstvariation of the second embodiment of the present invention. FIG. 9 is apartially enlarged view of a stator which relates to a second variationof the second embodiment of the present invention. FIG. 10 is apartially enlarged view of a stator which relates to a third variationof the second embodiment of the present invention. The above describedsecond embodiment deals with a case where a substantially rectangularrecess S11 is provided to the back yoke portion 175. The presentinvention however is not limited to such a case.

Specifically, as a stator 270 of a first variation shown in FIG. 8, therecess S21 to be formed in a portion of the back yoke portion 275 facingthe slot 277 may be formed so that the recess S21 is narrowed towardsthe both end portions relative to the Y-direction. Further, as a stator370 of a second variation shown in FIG. 9, the recess S31 to be formedin a portion of the back yoke portion 375 facing the slot 377 may beformed so that the both end portions of the recess S31 relative to theY-direction have substantially a circular shape. Provision of the recessS21 or S31 disturbs the flow of the magnetic flux; however, the flow ofthe magnetic flux is smoothened and the influence of the recess S21 orS31 is restrained by narrowing down the recess S21 or S31 towards itsboth end portions relative to the Y-direction, or by forming the recessS21 or S31 to have a circular shape at its end portions on the bothsides relative to the Y-direction.

Further, as a stator 470 of a third variation of the second embodimentshown in FIG. 10, two recesses S41 a and S41 b may be provided for asingle slot 477. In this case, by disposing the recesses S41 a and S41 bapart from each other by a predetermined distance in the Y-direction, aprotrusion S41 c is formed between the recesses S41 a and S41 b. Thisprotrusion S41 c supports the slot cell 73 disposed in the slot 477thereby preventing the slot cell 73 from being warped. As the result,the slot cell 73 is prevented from being warped while being disposed,even when the recesses S41 a and S41 b are provided in the portion ofthe back yoke portion 475 facing the slot 477. This third variation isparticularly advantageous in cases where the slot cell 73 is made of PETor the like whose Young's modulus is smaller than the aramid-basedresin, because the slot cell 73 made of such a material is easilywarped.

Third Embodiment

Next, with reference to FIG. 11, the following details a compressorrelated to a third embodiment of the present invention. Note that thefirst and the second embodiments deal with a case where a single slotcell (insulating member) insulates the coil from the core. The thirdembodiment however deals with a case of using two slot cells to insulatethe coil from the core. The third embodiment is the same as the firstembodiment except for the structure of a stator 570. Therefore, thedescriptions are omitted as needed.

<Core>

The core 71 is the same as that of the first embodiment, and is formedby laminating a plurality of thin metal plates and welding these platesto one another. As shown in FIG. 11, the core 71 has an annular backyoke portion 75, a plurality of tooth portions 76 each projectinginwardly from the back yoke portion 75 in a radial direction(X-direction), and a slot 77 formed between tooth portions 76 adjacentto each other.

Here, in the present embodiment, the slot 77 has therein two slot cells573A and 573B for insulating the core 71 from the coil 72. These slotcells 573A and 573B are laminated to each other. In the presentembodiment, the slot cell 573A (0.1 mm to 0.5 mm in thickness) on theside of the coil 72 (hereinafter, inner side) is made of a PET film,whereas the slot cell 573B (0.1 mm to 0.5 mm in thickness) on the sideof the core 71 (hereinafter, outer side) is made of an aramid-basednonwoven fabric.

Note that the “aramid-based” means a polyamide fiber in the aromaticseries.

That is, the slot cell 573B made of an aramid-based nonwoven fabricwhose Young's modulus is greater than the slot cell 573A on the innerside and which excels in the strength and durability is disposed on theouter side. Since the slot cell 573B with a greater Young's modulus isdisposed on the outer side, the portion of the slot cell 573B facing theinner circumference of the back yoke portion 75 extends straight alongthe direction ((Y-direction) perpendicularly crossing the radialdirection (X-direction), instead of being formed to be disposed alongthe inner circumference of the back yoke portion 75 in an arc-shape.This way, a gap S5 is provided between the inner circumference of theback yoke portion 75 and the inner circumference of the slot cell 573B.

[Characteristics of the Compressor of the Present Embodiment]

The compressor of the present embodiment has the followingcharacteristics.

In the compressor of the present embodiment, the gap S5 is providedbetween the back yoke portion 75 and the slot cell 573B. This restrainsthe welding heat from being transferred to the slot cell 573B. As theresult, melting of the slot cells 573B and 573A is restrained.

Further, in the compressor of the present embodiment, the slot cell 573Bon the outer side is made of an aramid-based nonwoven fabric whoseYoung's modulus is greater than PET which is typically used as thematerial for a slot cell. This way the slot cell 573B on the outer sideis hardly warped. Thus, the slot cell 573 having the slot cell 573B andthe slot cell 573A on the inner side is not disposed along the back yokeportion 75 in the slot 77, and the gap S5 is formed between the backyoke portion 75 and the slot cell 573. Thus, by simply changing thematerial for the slot cell 573B on the outer side, the gap S5 forrestraining heat transfer to the slot cell 573B is easily formed withoutchanging the shape of the core 71.

Further, the compressor of the present embodiment uses the two slotcells 573A and 573B which are laminated to each other. This realizes animproved dielectric strength as compared with a case of using a singleslot cell having a similar thickness.

Further, in the compressor of the present embodiment, the reliability isimproved by the slot cell 573B made of an aramid-based nonwoven fabricwhich is excellent in the strength and the durability. Specifically,using an aramid-based nonwoven fabric as a material for the slot cell573B on the outside which is more easily influenced by the welding heatimproves the reliability of the compressor.

In a compressor using a slot cell 573B made of an aramid-based nonwovenfabric having a high elasticity, the slot cell 573B is firmly disposedby arranging a slot cell 573A on the inner side of the slot cell 573B topress the slot cell 573B, the slot cell 573A being made of a PET filmwhich is flexible and easily disposed along the shape of the slotaramid-based nonwoven fabric. This restrains the slot cell 573B frombeing enwound at the time of winding.

Further, the cost of the PET film is lower than that of an aramid-basedresin. Therefore, the PET film is more advantageous in terms of costthan laminating slot cells made of an aramid-based nonwoven fabric.

The above describes embodiments of the present invention, with referenceto the drawings. The specific structures however shall not be limited tothese embodiments. The scope of the present invention is indicated notonly by the above embodiments, but also by the claims set forthhereinbelow. The scope of the present invention encompasses all themodifications and equivalents in the meaning within the scope of theclaims.

For example, the above embodiments deal with a case of applying thepresent invention to a 2 cylinder compressor; however, the presentinvention is not limited to this. The present invention is applicable toa 1 cylinder compressor or a 3 cylinder compressor.

Further, the above embodiments deal with a case of a compressor using aCO₂ refrigerant; the present invention however is not limited to this.The present invention is also applicable to a compressor that adopts arefrigerant other than a CO₂ refrigerant.

The second embodiment deals with a case of adopting a slot cell using aPET film. The present invention however is not limited to this. Thematerial of the slot cell is not limited to PET as long as a gap isprovided between the back yoke portion and the slot cell.

Further, the above embodiments deal with a case where the winding methodof the coil of a motor is a concentrated winding. The present inventionhowever is not limited to this. The present invention is also applicableto a motor with a coil whose winding method is a distributed winding.

Further, the above embodiments deal with a case where the recess S11extends in a direction (Y-direction) perpendicularly crossing the radialdirection (X-direction) in a plan view. The present invention however isnot limited to this, as long as the recess S11 extends in a directioncrossing the radial direction (X-direction).

Further, the third embodiment deals with a case of adopting two slotcells. The present invention however is not limited to this, and threeor more slot cells may be adopted. In such a case, the slot cell closestto the coil is preferably made of PET, and the slot cell closest to thecore is preferably made of an aramid-based resin.

Further, the third embodiment deals with a case where the core is thesame as that used in the compressor of the first embodiment. The presentinvention however is not limited to this, and a plurality of slot cellsmay be disposed in a slot of a core having any of the recesses describedin the second embodiment and the variations of the second embodiment.

INDUSTRIAL APPLICABILITY

The present invention realizes a compressor in which melting of aninsulating member disposed in a slot is restrained.

REFERENCE SIGNS LIST

-   1 Compressor-   11 Pipe (Casing)-   20 Motor-   70, 170, 270, 370, 470, 570 Stator-   71, 171 Core-   72. Coil-   73, 173, 573A, 573B Slot cell (Insulating member)-   75, 175, 275, 375, 475 Back yoke portion-   76, 176 Tooth portion-   77, 177, 277, 377, 477 Slot-   S1, S5 Gap-   S11, S21, S31 Recess-   P1, P2, P3, P11 Weld position

1. A compressor comprising: a casing; and a motor disposed inside thecasing, the motor being welded to the casing at a plurality of weldpositions, the motor including: a core having an annular back yokeportion, a plurality of tooth portions projecting radially inwardly fromthe back yoke portion, and a slot formed between the tooth portionsadjacent to each other, a coil disposed in the slot, at least oneinsulating member disposed in the slot to insulate the coil from thecore, and a gap provided between the back yoke portion and theinsulating member.
 2. The compressor, according to claim 1, wherein aportion of the back yoke portion facing the slot is substantiallyarc-shaped.
 3. The compressor, according to claim 1, wherein theinsulating member is made of an aramid-based resin.
 4. The compressor,according to claim 1, wherein the at least one insulating memberincludes two or more insulating members which laminated to each other;and one of the insulating members closest to the core is made of anaramid-based resin.
 5. The compressor, according to claim 4, wherein atleast one of the insulating members disposed on an inner side of theinsulating member is made of an aramid-based resin is made of apolyethylene terephthalate film.
 6. The compressor, according to claim1, wherein recesses are formed in portions of the back yoke portion witheach recess facing the slot.
 7. The compressor, according to claim 6,wherein each of the recesses is provided only in a portion correspondingto a corresponding one of the weld positions relative to the up/downdirection.
 8. The compressor, according to claim 6, wherein in a planview, each of the recesses extends in a direction crossing a radialdirection, and is formed in such a manner that the recess is narrowedtowards its both end portions relative to the direction crossing theradial direction, or that the both end portions have a circular shape.9. The compressor, according to claim 6, wherein the casing has a weldhole provided at each of the weld positions; and in a plan view, widthsof the recesses relative directions crossing radial directions aregreater than widths of the weld holes relative to the directionscrossing the radial directions.
 10. The compressor, according to claim6, wherein each slot has more than one of the recesses.
 11. Thecompressor, according to claim 1, wherein the coil is a concentratedwinding.
 12. The compressor, according to claim 1, wherein a CO₂refrigerant is used in the compressor.